1. Field of the Invention
The present invention relates to a helicopter icing spray system, particularly an airborne icing system that is installed on the test aircraft so that its component parts can be tested under appropriate icing conditions.
2. General Background
The efficient design, instrumentation and testing of air induction systems to demonstrate compliance with the requirements of Appendix C of CFR continues to be one of the challenges of the aerospace industry. Not only must the design be of sufficient flexibility to accommodate the various potential flows and air pressures demanded by the dependent turbine engine, it often must serve as a shield and centrifugal flow separator to channel undesirable foreign objects away from the engine inlet.
Traditionally, most of the work for Appendix C certification has been done using ice tunnels and/or stationary super cooled water droplet generators. A typical ice test, therefore, required long lead times because of ice tunnel scheduling or was dependent on local weather conditions. This often resulted in unacceptable time delays as well as very expensive testing.
U.S. Pat. No. 4,799,390 issued to Kabushiki-Kaisha on the application of C. Kimura teaches a snow-weather test apparatus having a low temperature testing chamber and a water spraying unit with injection nozzles for spraying water with an air jet into a mist, the spraying unit being movably provided in the low temperature testing chamber.
U.S. Pat. No. 4,131,250 issued to E. T. Binckley discloses a helicopter with an external system mounted thereon to spray a freezing point depressant fluid. The freezing point depressant fluid is sprayed onto the main rotor blade to prevent the collection of ice when flying through icing weather.
U.S. Pat. Nos. 4,748,817; No. 4,755,062; No. 3,908,903; No. 4,723,707; and, No. 4,833,660 are other prior art patents in the general field.
In recent years the use of airborne icing systems (AISS) to accomplish testing have also been employed. Normally, these devices are installed in another aircraft and the test aircraft is flown in the spray pattern produced by the AISS. These systems require considerable support, highly trained personnel and often provide only a limited coverage of the test aircraft. The U.S. Army Aviation Engineering Flight Activity (USAAEFA) publication entitled Helicopter Icing Spray System (HISS) Evaluation and Improvements, April 1986, discusses such systems with respect to helicopters.